Suppose z is a standard normal variable. Find the value of z in ...

[jrubin]

Suppose z is a standard normal variable. Find the value of z in the following.
 a. The area between 0 and z is .4678.
  b. The area to the right of z is .1112.
  c. The area to the left of z is .8554
  d. The area between z and z is .754.
  e. The area to the left of z is .0681.
  f. The area to the right of z is .9803.

Question 2

A random sample of 49 lunch customers was selected at a restaurant. The average amount of time the customers in the sample stayed in the restaurant was 33 minutes. From past experience, it is known that the population standard deviation equals 10 minutes.
 a. Compute the standard error of the mean.
  b. What can be said about the sampling distribution for the average amount of time customers spent in the restaurant? Be sure to explain your answer.
 c. With a .95 probability, what statement can be made about the size of the margin of error?
  d. Construct a 95 confidence interval for the true average amount of time customers spent in the restaurant.
 e. With a .95 probability, what sample size would have to be selected to provide a margin of error of 2.5 minutes or less?

[mohan]

Answer to Question 1

a. 1.85
b. 1.22
c. 1.06
d. 1.16
e. 1.49
f. 2.06

Answer to Question 2

a. 1.4286
b. Normal by the central limit theorem
c. There is a .95 probability that the sample mean will provide a margin of error of 2.80 or less.
d. 30.20 to 35.80
e. 62

[jrubin]

Thanks for the timely response, appreciate it

[xiaomengxian]

Excellent